DNA repair mechanisms are essential for maintaining genome integrity following events that damage DNA. Double strand breaks induced by ionizing radiation are detrimental to human cells and are repaired by proteins that identify the broken ends and then ligate them back together. Cellular DNA repair mechanisms are activated by Adenovirus (Ad) mutants, which have a linear double strand DNA genome and fail to express regulatory proteins from early region 4. Our broad objectives are to understand 1) what characteristics of Ad genomes, viral gene expression, or DNA replication activities are important for activating a cellular DNA damage response, 2) how do DNA damage response sensor and transducer proteins respond to these viral signals, and 3) how do viral proteins interfere with DNA damage responses. We expect our results to identify characteristics and activities of Ad genomes that are important for triggering cellular DNA repair responses. This is relevant to our understanding of how DNA repair processes maintain genome integrity and prevent damaged cells from developing into cancer cells. Our results will also be important for understanding how Ad vectors used in gene expression or gene therapy studies may interact with DNA repair responses in the cells they infect. These vectors are frequently replication-defective, but nonetheless introduce double stranded linear DNA genomes into the cell, potentially activating aspects of the DNA damage response that do not require viral DNA replication. Understanding these activities will be important as new Ad vectors are designed and implemented for gene expression and gene therapy. We will investigate the ability of different damage signals generated by Ad infection to activate different DNA damage response pathways. This should provide important information regarding the ability of signal-transducing kinases to react to different types of damage signals. Finally our results are expected to provide further insight into the ability of Ad proteins to interfere with DNA damage responses thereby potentially elucidating new mechanisms used by Ad to block this obstacle to a productive infection. The results of these studies will help us understand mechanisms involved in activating and inactivating cellular DNA repair responses during Ad infection, and how DNA damage responses are coordinated to potentially multiple DNA damage signals generated during Ad infection. PUBLIC HEALTH RELEVANCE: The ability of cells to respond to and repair DNA damage is critical for their ability to maintain their genome integrity, and avoid developing mutations or chromosome abnormalities that could result in cancer. It is therefore important to understand the mechanism that cells use to identify and respond to DNA damage events. This proposal seeks to understand how a virus infection controls activation of DNA damage responses. We will use this as a model system to understand why the cell perceives and responds to this virus as DNA damage, and to also understand what strategies the virus employs to prevent the cell from perceiving it.